During machining, in particular of materials that are difficult to machine and of labile components such as those often used in modern engine construction, as a rule there occur systematic positional and shape deviations that are caused primarily by the internal stress of the material and by pressure displacement of the tool or of the workpiece due to their elastic deformation. During processing using NC-controlled machines, these errors have the result that the milled geometry deviates from the programmed geometry, thus lying outside the tolerances according to the drawing.
When the existing material internal stresses of a workpiece are dismantled by milling, there often occur torsions or warpings that can assume significant dimensions depending on the component geometry, and that have the result that the geometry of the workpiece lies outside manufacturing tolerances. In addition, the tool and/or the workpiece are pressed out of the target position by the machining forces. The magnitude of the pressure depends essentially on the machining force and on the rigidity of the overall system consisting of the workpiece, the tool, and the machine.
These are undesirable effects that result in a high rejection rate, a high post-processing expense, and, therefore, increased manufacturing costs and high piece costs.
In addition, from the prior art NC-controlled cutting production machines are known. As a rule, in such machines the NC programs are nominally pre-programmed, during their creation, with the corresponding parameters, such as the positional and geometric data of the workpiece to be processed, and additional data such as data relating to, for example, advance speed and cutting speed.
In addition, for example from U.S. Pat. No. 4,660,148, input modules are known that are intended to permit certain data inputs to the NC machine to be made on location by an operator, including the inputting of non-variable data and geometric data of the workpiece. Here, positional and/or shape deviations due to material characteristics and/or tool characteristics are not taken into account.
Therefore, the object of the present invention is to provide an improved method and an improved device for compensating positional and shape deviations that avoid the disadvantages of the prior art, thus providing an economical solution with a reduced manufacturing expense.